Degeneration of the fibrocartilaginous menisci has long been associated with chondral degeneration in advanced osteoarthritis (OA) of the knee, but the relationship between meniscal degeneration in the onset and progression of knee OA remains unclear. Meniscal tears have long been recognized as a contributing factor to knee OA, primarily due to changes in joint biomechanics that result in local increases or decreases in the mechanical stresses on the cartilage. However, a variety of recent findings suggest that degenerative meniscal changes, regardless of whether or not tears are present, may be an early event in the development of idiopathic knee OA. Despite the growing indications of the importance of asymptomatic meniscal degeneration, relatively little is currently known regarding the mechanisms contributing to meniscal degeneration or the reasons why meniscal lesions appear to precede cartilage degeneration. The proposed studies will investigate the effects of biochemical and biomechanical induction of meniscal degradation. Aim 1 will examine the progression of meniscal degradation induced by exogenous Interleukin-l (IL-1) to test the hypothesis that the accelerated meniscal response to IL-1 involves proteolytic processes active in cartilage degradation and is dispersed throughout both inner (compression) and outer (tension) zones. Aim 2 will examine the progression of meniscal degradation induced by compressive overload to test the hypothesis that moderate compressive overload of meniscal explants will induce cell-mediated matrix degradation involving the same catabolic processes induced by IL-1 stimulation. Aim 3 will examine the ability of aggrecanase inhibition to protect the meniscal matrix from degradation to test the hypothesis that prevention of aggrecan depletion will protect the collagen from proteolytic degradation. These studies will provide important new insights into the progression of meniscal degeneration and could lead to novel diagnostic or therapeutic targets to prevent or delay the progression of OA.